Update git submodules
- Update extensions/TitleBlacklist from branch 'REL1_39' to 2c8c4f23384d43a75e6b21d797862c9fa839400c
- build: Update MediaWiki requirement to 1.39.0
Change-Id: I3165a1c0cb16fa18f16f5eb8f7667d6eb26d1317
- build: Update MediaWiki requirement to 1.39.0